Combined service and parking brake

ABSTRACT

A disk brake assembly for a motor vehicle in which the friction pads are applied by a spring force in addition to being hydraulically actuated. A fluid pressure release system is employed for releasing the spring actuated portion of the brake. This brake may, therefore, function as a combined service and parking brake with the spring applied portion serving as the parking brake.

United States Patent 1191 Evans I COMBINED SERVICE AND PARKING AnthonyC. Evans, Westland, Mich.

Kelsey-Hayes Company, Romulus, Mich.

Filed: Jilly 21, 1970 Appl. No.: 56,921

Inventor: v

Assignee:

us. c1. I. ..188/106 P, 188/719, 188/170, 188/196 1) [58] Field ofSearch ..l88/71-.9, 106 R, 188/106 F, 106 P, 170, 196 D [56] 9References Cited UNITED STATES PATENTS 2,914,144 11/1959 Hovell..l88/l70X 3,378,109 4/1968 Bauman ..l88/7l.9

1 1 Apr. 10, 1973 Primary Examiner-Duane A. Reger Attorney-Harness,Dickey & Pierce ABSTRACT A disk brake assembly for' a motor vehicle inwhich the friction pads are applied by a spring force in addition tobeing hydraulically actuated. A fluid pressure release system isemployed for releasing the spring actuated portion of the brake. Thisbrake may, therefore, function as a combined service and parking brakewith the spring applied portion serving as the parking brake.

12 Claims, 3 Drawing Figures I 1 COMBINED SERVICE AND PARKING BRAKEBACKGROUND OF THE INVENTION with spring application have beencomplicated ancl expensive. In addition, such brakes have not permittedthe incorporation of devices for automatically compensating for liningwear.

It is, therefore, a principal object of this invention to provide animproved and simplified brake assembly that may be applied bothhydraulically and by means of spring pressure.

It is another object of this invention to provide a combined spring andfluid pressure applied brake incorporating an automatic adjustingmechanism.

Although all motor vehicles are equipped with parking brakes, mostoperators rarely use the parking brake. Generally, the operator reliesupon the use of the transmission to prevent the vehicle from rollingwhen it is not being operated. That is, when the vehicle is parked, theoperator generally leaves the transmission in gear or in a specialparking range provided for this purpose. Doing so without applying theparking brake places a considerable strain on the transmission andaffords no safety factor in the event the transmission or drive trainshould break.

It is, therefore, another object of this invention to provide a brakesystem for a motor vehicle that automatically engages when the vehicleis not being driven.

SUMMARY OF THE INVENTION are nested within the piston and have anoperative connection with the piston and with the housing for exertingan actuating force upon the piston. Release means are provided forrelieving the piston of the actuating force of the spring means.

Still a further feature of this invention is adapted to be embodied in abrake system for a self-propelled vehicle. The brake system includes avehicle wheel brake having a brake shoe for braking the rotation of avehicular wheel. A primary brake actuating system is provided fornormally actuating the brake shoe. Parking brake means responsive to thecessation of operation of the vehicle engine are provided for'applyingthe brake shoe when the vehicle engine ceases to operate.

Means are additionally provided that are responsive to the operation ofthe vehicle engine for disabling the parking brake means whereby thebrake shoe may be normally operated by the primary brake actuatingsystem.

I BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view, with aportion broken away, of a vehicle wheel brake embodying this inventionand showing a portion of the system in schematic form.

FIG. 2 is an enlarged cross-sectional view taken along the line 2-2 ofFIG. 1.

This invention is adapted to be embodied in a disk brake assembly. Thebrake assembly includes a housing.

biasing means. Released means are provided for relieving the piston fromthe actuating force of the biasing means for normal fluid pressureoperation of the brake. Automatic adjusting means are provided in theoperative connection between thebiasing means and the piston foradjusting the at rest position of the piston when the piston isnotactuated by the biasing means or by fluid pressure in the bore.

Another feature of the invention is adapted to be embodied in a compactdisk brake assembly. Such an as sembly includes a housing that defines abore and a piston that is slidably supported within the bore. The

v bore is adapted to be exposed to fluid pressure for actuating thepiston and bringing an associated brake pad into frictionalengagementwith a rotor. Spring means FIG. 3 is a cross-sectional view,in part similar to FIG. 1, showing another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention isadapted to be embodied in a selfpropelled motor vehicle such as anautomobile. The invention may be applied to at least two of the vehiclewheel brakes, one of which is shown in FIG. 1 and is identifiedgenerally by the reference numeral 11. The brake ll is of the disk typeembodying a dual piston, sliding caliper arrangement which may be of anyknown type except as hereafter noted. The brake 11 includes a rotor 12that is affixed for rotation with a vehicular wheel (not shown) andwhich defines oppositely facing braking surfaces 13 and 14. A pair ofbrake pads 15 and 16 is disposed adjacent the rotor braking surfaces 13and 14, respectively. The brake pad 15 is engaged by a pair of pistons17 and 18 that are carried by a caliper assembly indicated generally bythe reference numeral 19 in a manner which will become more apparent asthis description proceeds. The caliper assembly 19 includes a leg 21that is engaged with the brake pad 16. As is well known with the slidingcaliper type of disk brake, when the pistons 17 and 18 are actuated, thecaliper 19 will slide and the leg 21 will exert an applying forceagainst the brake pad 16.

Theactuating structure and each of the pistons 17 The chamber 23 isadapted to be selectively applied with fluid under pressure from amaster cylinder (not shown) for actuating the piston 18.

An internally threaded sleeve, indicated generally by the referencenumber 24, has a cylindrical portion 2% that is slidably received in abore 26 formed in the caliper 19 at the base of the bore 22. The sleeve24 has internal threads 27 that are engaged with threads 28 of anadjusting member 29. The adjusting member 29 has an enlarged headportion 31 that is juxtaposed to a rear wall 32 of the piston 18. Theadjusting member 29 is located axially with respect to the piston 18 bymeans of a collar 33 that is affixed to the piston 18 by means of screws34 (only one of which appears in the drawings). An anti-friction thrustbearing 35 is interposed between the collar 33 and the adjusting memberheaded portion 31. A torsional spring 36 encircles the headed portion 31and is affixed to one of its ends to the piston 18 which acts as a oneway clutch between the piston 18 and the adjusting member 29.

The sleeve 24 is held against rotation by means of a washer 37. Thewasher 37 has an opening 38 which is defined in part by a pair of flats39 and 41 (FIG. 2) that engage cooperating flats 42 and 43 fonned on thesleeve 24 at one end of the cylindrical portion 25. The washer 37 isformed with a tang 44 that is received in a drilled hole 45 formed witha tang 44 that is received in a drilled hole 45 formed in the caliper 19at the base of the bore 22.

A plurality of Belleville springs 46 is nested within the piston 18 andencircles a circular portion 47 of the sleeve 24 formed adjacent theflats 39 and 41. The Belleville springs 46 bear against a shoulder 48formed on the sleeve 24 and against the caliper 19 at the base of thebore 22 through the washer 37. Thus, the Belleville springs 46 exert abias on the sleeve 24 that tends to urge the sleeve 24 and adjustingmember 29 toward the rotor braking surface 13.

An auxiliary piston 51 is formed with a tapped opening 52 that isthreaded onto a male threaded section 53 formed at the other end of thesleeve 24. The auxiliary piston 51 carries an O-ring seal 54 thatslidably engages a bore 55 formed in the caliper l9 concentrically withthe bore 22. The bore 55 forms with the piston 51 a fluid chamber 56.The chamber 56 is adapted to receive a fluid under pressure, for areason which will become more apparent as this description proceeds. Thechamber 56 may be pressurized in one of several different methods, aswill be described. For the sake of illustration a conduit 57 extendsfrom a source of fluid under pressure, indicated schematically at 58 tothe chamber 56. A dust seal 59 has a bead 61 that is received in agroove 62 formed at the outer periphery at the caliper 19 and adjacentthe bore 55. The dust seal 59 encircles the auxiliary piston 51 andprotects it from contamination.

OPERATION The brake assembly 11 is adapted to be actuated hydraulicallythrough pressurization of the bore 22 for normal service brakeoperation. In addition, the brake assembly 11 may be spring applied, bymeans of the Belleville springs 46 for parking brake application. Torelease the parking brake, the chamber 56 is pressurized. Thispressurization may be obtained in any suitable manner. For example, thepressure that is transmitted to the chamber 56 may be derived from anengine driven pump and in a circuit that includes an accumulator. Inorder to apply the parking brake, the pressure in the chamber 56 isrelieved so that the springs 46 may actuate the pistons 17 and 18, aswill be I described. One way in which the brake assembly 11 may be usedwill achieve automatic parking brake operation. In such a system, thepressure source 58 may comprise a pump that is driven by the engine sothat it will generate a pressure at all times the engine is running.

The drawings illustrate the brake assembly 11 as it appears when thevehicle engine is not running. Under this condition, there issubstantially no fluid pressure in the chamber 56 and the Bellevillewashers 46 acting through the sleeve 24 and adjusting member 29 urge thepistons 17 and 18 toward the rotor braking surface 13. This force issufficient to hold the brake pad 15 in frictional engagement with therotor braking surface 13. At the same time, a reactive force is exertedupon the caliper 19 that causes it to shift and move the leg 21 towardthe rotor braking surface 14. This force is transmitted to the brake pad16 to bring it into frictional engagement with the rotor braking surface14. Hence, the brake pads 15 and 16 will be held in tight frictionalengagement with the respactive rotor braking surfaces and will hold therotor 12 against rotation. The one way clutch between the piston 18 andadjusting member 29 precludes any rotation of the adjusting member 29when the springs 46 apply the brake.

When the engine of the associated vehicle is in operation, the enginedriven auxiliary pump 58 will deliver fluid under pressure through theconduit 57 to the chamber 56. This pressurization will be sufficient tourge the auxiliary piston 51 away from the rotor braking surface 15.Since the auxiliary piston 51 is connected to the sleeve 24, the sleeve24 and the adjusting member 29 will be moved away from the rotor brakingsurface 13. The movement of the adjusting member headed portion 31 istransmitted through the thrust bearing 35 and washer 33 to the pistons17 and 18. During this action the Belleville springs 46 are compressedand the force that they previously exerted on the caliper 19 is overcomeby the pressure in the chamber 56. Hence, when the engine is running,the brake pads 15 and 16 only have light rubbing contact with the rotor12 as is well known in this art.

When it is desired to operate the brake assembly 11, the fluid chamber23 is pressurized in any known manner. This pressure acting on thepistons 17 and 18 causes them to shift toward the rotor braking surface13. The brake pads 15 and 16 will then be applied to the rotor brakingsurface 13 and 14. When the fluid pressure in the chamber 23 isrelieved, a seal 66 positioned around the bore 22 acts on the piston 18to release it, as is well known in this art. An axial clearance existsbetween the trapped, adjusting member headed portion 31 and the piston18 to permit normal actuation and release of the piston 18.

In the event there has been more than a predetermined degree of liningwear on the brake pads 15 and 16, which degree of permissible wear isdetermined by the aforenoted clearance, the adjusting member 29 will beadjusted upon actuation of the piston 18. When the brake pads areapplied by pressurizing the chamber 23 and adjustment is required, aforce will be exerted on the adjusting member 29 that causes it torotate. This rotation is permitted by the spring clutch 36. Since thesleeve 24 is held against rotation, an adjustment will be made in the atrest position of the member 29. When the pressure in the chamber 23 isrelieved, the pistons 17 and 18 will be retracted by the seals 66interposed between the bore 22 and the pistons 17 and 18 to the new atrest position determined by the position of the adjusting member 29.Thus, adjustment of the at rest position of the brake assembly isaccomplished automatically.

In the described embodiment, the brake assembly 11 was automaticallyengaged when'the engine was not running. Under some conditions it may bedesired to permit release of the brake when the engine is not running.Such an arrangement is shown in the embodiment illustrated in FIG. 3.Except for the structure to be described, this embodiment is the same asthe embodiment of FIG. 1 and FIG. 2 and the description of the overallconstruction will not be repeated.

In this embodiment, thesleeve 24 has a reduced diameter portion 72 thatextends through a bore 73 in the auxiliary piston 51. A nut 74 isreceived on a threaded end 75 of the sleeve portion 72. The piston 51 isnormally held against a washer 76 that is interposed between the piston51 and the nut 74. Thus, when the chamber 56 is pressurized, the motiontransmitted to the piston 51 will be transmitted through the nut 74 andwasher 76 to the sleever 24. Also, when the Belleville washers act onthe sleeve 24, this motion will be transmitted through the nut 74 andwasher 76 to the piston 51. The brake pads in this embodimentare'operated in the same manner as previously described.

FIG. 3 illustrates the brake with the engine no running and the brakeapplied by the Belleville washers 46. If it is desired to release thebrakes, the nut 74 is turned so that it will advance on the thread 75and urge the piston 51 to the left as viewed in FIG. 3. This movement iscontinued until the piston 51 abuts a wall 77 of the caliper 19. At thistime, further movement of the piston 51 is precluded. Continued rotationof the nut 74 will cause the sleeve 24 to move to the right as viewed inthis figure. This movement is transmitted through the adjusting member29 to the pistons 17 and 18 with a resulting release of the brake pads15 and 16.

The operation of the embodiments of FIGS. 1 and 2 and FIG. 3 has beendescribed in connection with an automatically applied parking brake. Ashas, been previously noted, the parking brake may be applied in othermanners than automatically. For example, an engine driven pump or anelectrical pump may charge the system 58 and provide the pressure foractuating the auxiliary piston 51. The pressure in the chamber 56 may berelieved to cause spring application at the desired times, in any knownmanner.

, It is to be understood that the foregoing description is that ofpreferred embodiments of the invention. Various changes andmodifications may be made without departing from the spirit and scope ofthe invention as defined by the appended claims.

lclaim: l. A disk brake assembly comprising a housing defining a bore, apiston slidably supported within said bore,

' said bore being adapted to be exposed to fluid pressure for actuatingsaid piston to bring an associated brake pad into frictional engagementwith a rotor, spring means nested within said piston, said spring meanshaving an operative connection with said piston and said housing forexerting an actuating force upon said piston, and release means forrelieving said piston from the actuating force of said spring means fornormal fluid pressure operation of said brake assembly.

2. A disk brake assembly as set forth in claim 1, wherein the operativeconnection between the spring means and the piston includes automaticadjusting means for adjusting the at rest position of said piston.

3'. A disk brake assembly as set forth in claim 2, wherein the automaticadjusting means includes a threaded connection, the operative connectionbetween the spring meansand the piston including an adjusting memberhaving a lost motion connection with said piston.

4. A disk brake assembly as set forth in claim 1,

wherein the release means comprises a fluid operated piston.

5. A disk brake assembly as set forth in claim 4, wherein the fluidoperated piston of the release means is supported within a second borein the housing concentric and spaced from the first bore.

6. A disk brake assembly including a rotor having a braking surface, abrake pad juxtaposed to said rotor and adapted to frictionally engagesaid rotor braking surface, a caliper defining a cylindrical bore, apiston slidably supported in said cylindrical bore and adapted tooperate said braking pad for bringing said brake pad into frictionalengagement with said rotor braking surface, an adjusting memberoperatively associated with said piston and having a threaded portion, athreaded member matingly engaged with said threaded portion of saidadjusting member, a spring means interposed between said caliper andsaid threaded member for urging said threaded member, said adjustingmember and said piston to a brake pad applying position, an auxiliarypiston affixed to said threaded member, means for applying fluidpressure to said auxiliary piston for moving said threaded member andcompressing said spring means for precluding spring application of saidbrake pad, and means for manually relieving the force applied by saidspring means to said piston for preventing spring actuation of the brakepad.

7. A disk brake assembly as set forth in claim 6 wherein the means formanually relieving the force exertedby the spring means includes athreaded member engageable with an abutment.

8. A disk brake assembly as set forth in claim 6 wherein the means formanually relieving the force of the spring means includes means forexerting an axial force on the threaded member in opposition to theforce exerted thereupon by the spring means.

9. A disk brake assembly as set forth in claim 6 further includingmanually operable release means for relieving the force exerted by thespring means upon the piston.

10. A disk brake assembly as set forth in claim 6 wherein the springmeans comprise a plurality of Belleville springs.

11. A disk brake assembly as set forth in claim 10 wherein the automaticadjusting means includes a female threaded member extending from thefirst bore to the second bore, the fluid operated piston of the releasemeans being connected to said female threaded member and the Bellevillespring means encircling said female threaded member.

the actuating force exerted by the spring means on the brake pad inresponse to the application of fluid pressure thereto, and means formanually relieving the pressure exerted by the spring means on the brakepad for releasing the brake pad manually upon failure of the secondfluid motor.

1. A disk brake assembly comprising a housing defining a bore, a pistonslidably supported within said bore, said bore being adapted to beexposed to fluid pressure for actuating said piston to bring anassociated brake pad into frictional engagement with a rotor, springmeans nested within said piston, said spring means having an operativeconnection with said piston and said housing for exerting an actuatingforce upon said piston, and release means for relieving said piston fromthe actuating force of said spring means for normal fluid pressureoperation of said brake assembly.
 2. A disk brake assembly as set forthin claim 1, wherein the operative connection between the spring meansand the piston includes automatic adjusting means for adjusting the atrest position of said piston.
 3. A disk brake assembly as set forth inclaim 2, wherein the automatic adjusting means includes a threadedconnection, the operative connection between the spring means and thepiston including an adjusting member having a lost motion connectionwith said piston.
 4. A disk brake assembly as set forth in claim 1,wherein the release means comprises a fluid operated piston.
 5. A diskbrake assembly as set forth in claim 4, wherein the fluid operatedpiston of the release means is supported within a second bore in thehousing concentric and spaced from the first bore.
 6. A disk brakeassembly including a rotor having a braking surface, a brake padjuxtaposed to said rotor and adapted to frictionally engage said rotorbraking surface, a caliper defining a cylindrical bore, a pistonslidably supported in said cylindrical bore and adapted to operate saidbraking pad for bringing said brake pad into frictional engagement withsaid rotor braking surface, an adjusting member operatively associatedwith said piston and having a threaded portion, a threaded membermatingly engaged with said threaded portion of said adjusting member, aspring means interposed between said caliper and said threaded memberfor urging said threaded member, said adjusting member and said pistonto a brake pad applying position, an auxiliary piston affixed to saidthreaded member, means for applying fluid pressure to said auxiliarypiston for moving said threaded member and compressing said spring meansfor precluding spring application of said brake pad, and means formanually relieving the force applied by said spring means to said pistonfor preventing spring actuation of the brake pad.
 7. A disk brakeassembly as set forth in claim 6 wherein the means for manuallyrelieving the force exerted by the spring means includes a threadedmember engageable with an abutment.
 8. A disk brake assembly as setforth in claim 6 wherein the means for manually relieving the force ofthe spring means includes means for exerting an axial force on thethreaded member in opposition to the force exerted thereupon by thespring means.
 9. A disk brake assembly as set forth in claim 6 furtherincluding manually operable release means for relieving the forceexerted by the spring means upon the piston.
 10. A disk brake assemblyas set forth in claim 6 wherein the spring means comprise a plurality ofBelleville springs.
 11. A disk brake assembly as set forth in claim 10wherein the automatic adjusting means includes a female threaded memberextending from the first bore to the second bore, the fluid operatedpiston of the release means being connected to said female threadedmember and the Belleville spring means encircling said female threadedmember.
 12. A disk brake assembly for providing hydraulic and automaticspring operation of a brake pad comprising a first fluid motor having afirst piston operatively associated with the brake pad for actuating thebrake pad, spring means operatively associated with the brake pad forautomatically applying the brake pad, a second fluid motor having asecond fluid piston operatively associated with said spring means forrelieving the actuating force exerted by the spring means on the brakepad in response to the application of fluid pressure thereto, and meansfor manually relieving the pressure exerted by the spring means on thebrake pad for releasing the brake pad manually upon failure of thesecond fluid motor.